Position sensing devices, including inductive position sensors, are widely used today. Various uses include, but are not limited to, automobiles and other vehicles, factory settings, personal products, and otherwise. Inductive position sensors are often used to determine the position of an object, such as brake pedal, a throttle, or otherwise, hereafter defined as a “target.” Today, inductive sensors typically include an excitation coil configured to generate an electromagnetic field when electrical current flows through the coil, a receiving coil configured to detect an electrical potential, a voltage, induced in the receiving coil by the currents flowing through the excitation coil, and a rotor. The rotor is configured to disturb the amount of electrical potential induced in the receiving coil based on the rotor's position. The rotor is typically attached, directly or indirectly, to the target, such that as a target's position changes, the rotor's relative position also changes. Such changes in the position of the rotor, in turn, uniquely disturb the voltages induced in the receiving coil such that the position of the rotor, and thereby the target, can be determined based on the changes in the electrical potential induced in the receiving coil. In short, a rotor can be defined to affect the inductive coupling between the excitation coil and the receiving coil by mathematical functions (each a “transfer function”). Circuitry is connected to a receiving coil to detect and determine a rotor's relative position based on the relative amplitudes and changes thereof induced in the receiving coil.
One example of a known inductive position sensor is described in U.S. Pat. No. 9,528,858, which issued on Dec. 27, 2016, in the name of inventor Jacques Bertin, and entitled “Inductive Sensor,” the entire contents of which are incorporated herein by reference.
More specifically, inductive position sensors often use a single-turn receiving coil that is laid out in a rotational symmetry around one or more single turn or multi-turn excitation coils, collectively, a “stator.” As shown for example in FIG. 1A, a stator 100 often includes a first coil 101 that includes one or more first loops 101a-101n, and a second coil 102, commonly having only a multi-turns single loop. Both the first coil 101 and the second coil 102 are often drawn onto a single or multiple layer PCB 104. Either of the first coil 101 or second coil 102 may be respectively configured as excitation coils or receive coils. As shown, the first coil 101 commonly includes multiple loops 101a-100n drawn across one or more layers of the PCB 104. FIG. 1B provides a representation of a bottom view of the PCB 106 where loops 100a-110n of the first coil 101 are drawn. The second coil 102 can be configured in a clockwise or counter-clockwise pattern on the top or first layer, a second layer, or using multiple layers of a multi-layer PCB 104.
As shown in FIG. 1C, a common embodiment of a rotor 108 typically includes a rotor coil 110 with symmetry similar to the symmetry used with the first coil 101. The rotor coil 110 is often drawn such that it affects the mutual inductances generated between the first coil 101 and the second coil 102 as a function of the rotor's angular position Θ and in accordance with one or more transfer functions.
An electrical circuit 112 schematic representation of inductive position sensor is shown in FIG. 1D. The circuit 112 includes three first coils 101-1 to 101-3, functioning as excitation coils, where each coil has one or more loops (not shown). The first coils 101-1 to 101-3 are typically symmetrical and are often respectively offset from each other by 120 degrees, with each loop turning 90 degrees. The first coils 101-1 to 101-3 are connected to an alternating current source (not shown) that provides an alternating current, in sequence, to each of the three coils. Switching of each of the first coils 101-1 to 101-3 “on” and “off” is often accomplished using known devices, such as MOSFET transistors and oscillators (not shown). The circuit 112 also includes a second coil 102 functioning, as a receiving coil, connected to a signal processor (not shown). The signal processor is configured to detect changes in the amplitude of a voltage potential induced in the second coil 102 by the first coils 101-1 to 101-3. Based on the amplitudes detected and changes therein, the relative angular position of a rotor 110 can be determined.
More specifically, an alternating current flowing through the first coils 101-1 to 101-3 generates first electromagnetic fields, which are represented by first field lines 114-1 to 114-3. The first electromagnetic fields are influenced by the position of the rotor coil 110, such that the second coil 102 is induced to generate voltage potentials based on second, modified electromagnetic fields 116-1 to 116-3. The influence of the rotor 110 on the first electromagnetic field 114 such that the receiving coil 102 senses the second electromagnetic fields 116 is commonly defined as a rotor's “transfer function” that can be represented mathematically.
While today's inductive position sensors are generally reliable, they often require too much printed circuit board (PCB) space when compared to other components. For example, inductive position sensors today may utilize 11 mm2. In contrast, processors may utilize as little as 2-3 mm2. Today's inductive position sensor are also complex, requiring the drawing of multiple precise loops to form the second coil 102. Drawing the second coil requires additional PCB area hence additional cost. With processor costs now approaching sensor costs, reductions in the form factor and complexity of inductive position sensors are needed.
Further, electro-magnetic compliance requirements are becoming more stringent. Yet, with conventional inductive position sensors, stators 100 often are susceptible to generating or receiving undesired electromagnetic emissions. For example, when the second coil 102 is configured as an excitation element, it will function as antenna and emit undesired electromagnetic waves. Contrarily, when the second coil 102 is configured as a receiving element, it is often susceptible to external electromagnetic disturbances. Such disturbances may affect the accuracy and sensitivity of the sensor.
Accordingly, a need exists for inductive position sensors that address these and other needs. Such needs are addressed by one or more of the embodiments of the present disclosure.